In absolute terms, men’s legs produce more force than women’s, but the gap is considerably smaller than most people assume and far smaller than the gap seen in the upper body. Women’s lower-body strength typically reaches about two-thirds of men’s, compared with roughly half for the upper body. Once you adjust for differences in muscle mass and body size, the lower-body gap shrinks dramatically and, in some studies, vanishes altogether. The story gets more interesting from there, because “stronger” is not a single thing: endurance, injury resilience, training response, and how legs hold up over a lifetime all paint a more complicated and sometimes reversed picture.
The Gap Is Smaller in the Legs Than in the Arms
One of the most consistent findings across decades of research is that sex differences in strength are not uniform across the body. A widely cited study measuring both upper- and lower-body strength found that women were roughly 52% as strong as men in the upper body but about 66% as strong in the lower body.1PubMed. Gender differences in strength and muscle fiber characteristics That pattern holds up in younger populations too. A meta-analysis of children and adolescents found that the sex difference in upper-limb strength was significantly greater than the lower-limb difference across all age groups, and the gap widened most dramatically between ages 14 and 17.2PubMed Central. Sex Differences in Upper‐ and Lower‐Limb Muscle Strength in Children and Adolescents: A Meta‐Analysis
Why do the legs tell a different story than the arms? Partly because everyone uses their legs all day. Walking, climbing stairs, standing up from a chair: the legs get a baseline level of loading from daily life that the upper body simply does not. There is also an evolutionary angle. Skeletal analysis of Australian hunter-gatherer populations found virtually absent sexual dimorphism in lower-limb robusticity, consistent with ethnographic records showing equivalently high mobility among women and men, while upper-limb dimorphism was more pronounced.3PubMed. Robusticity and sexual dimorphism in the postcranium of modern hunter-gatherers from Australia In other words, the legs may be the body region where evolution has pushed men and women closest together, because both sexes needed to walk, run, and carry loads over long distances.
What Happens When You Account for Body Size
Raw strength numbers are misleading without context. Men tend to be taller and heavier with more lean mass, and much of the absolute strength gap simply reflects that size difference. A study of university students found that women’s strength corresponded to over 50% of men’s, while their lean mass was about 55% of men’s, and there was a strong relationship between the two.4PubMed Central. Sex differences in upper and lower strength and their association with body composition among university students So a large chunk of the gap is just a mass gap.
When researchers adjust for lean body mass, the lower-body difference often disappears entirely. One study of male and female athletes found no significant sex difference in one-rep-max squat, one-rep-max deadlift, or countermovement jump power after adjusting for lean body mass.5PubMed Central. A Comparison between Male and Female Athletes in Relative Strength and Power Performances Even when researchers go a step further and look at the force produced per unit of muscle cross-sectional area, the sex difference in knee extension strength also disappears.1PubMed. Gender differences in strength and muscle fiber characteristics That finding is meaningful: it suggests that a square centimeter of quadriceps muscle produces about the same force regardless of whether it belongs to a man or a woman. The muscle tissue itself is not weaker. There is just less of it.
Fiber Types and What They Mean for Endurance
Skeletal muscle is made of different fiber types, and men and women have them in different proportions. Two recent meta-analyses converge on the same pattern: women have a greater proportion of Type I (slow-twitch) fibers, while men have a greater proportion of Type II (fast-twitch) fibers.6PubMed Central. Sex differences in human skeletal muscle fiber types and the influence of age, physical activity, and muscle group: A systematic review and meta-analysis7PubMed. Sex differences in skeletal muscle fiber types: A meta-analysis Men also have larger fibers of both types, but the size advantage is especially pronounced in Type II fibers, which are the ones responsible for explosive power.
This fiber-type profile gives women a real advantage in muscular endurance. Type I fibers are more fatigue-resistant, rely more on aerobic metabolism, and recover faster. A study that had men and women perform repeated dynamic contractions found that men and women experienced similar fatigue in the elbow flexors, but men had significantly greater reductions in knee extensor force and muscle activation than women.8PubMed Central. Fatigue and recovery from dynamic contractions in men and women differ for arm and leg muscles That is a notable result: specifically in the legs, women’s muscles held up better under repeated loading. If your definition of “strong” includes the ability to keep producing force over time rather than just peaking once, women’s legs have a genuine edge.
Muscle Architecture and Tendon Properties
Strength is not just about how much muscle you have. How that muscle is built matters too. In the lower extremities, men have greater muscle thickness across all measured muscles, but fascicle length (the length of the individual muscle fibers) shows no sex difference.9PubMed Central. The relationship between muscle thickness and pennation angle is mediated by fascicle length in the muscles of the lower extremities Men do tend to have wider pennation angles, meaning their muscle fibers attach to tendons at steeper angles, which lets more fibers pack into a given space and generally increases force production. Researchers studying the ankle muscles specifically found that optimal pennation angles were significantly greater in men across all the primary plantar flexor and dorsiflexor muscles, and recommended that biomechanical models use sex-specific values.10Journal of Applied Biomechanics. Optimal Pennation Angle of the Primary Ankle Plantar and Dorsiflexors: Variations with Sex, Contraction Intensity, and Limb
Tendons also differ. A systematic review and meta-analysis found that both Achilles tendon stiffness and patellar tendon stiffness were significantly higher in men than in women.11PubMed Central. Sex-Related Differences in Human Tendon Stiffness: A Systematic Review and Meta-analysis Stiffer tendons transmit force more efficiently, which benefits power production. But more compliant tendons, like those more commonly found in women, may store and return elastic energy differently and could play a role in women’s endurance advantages. There has been speculation that hormonal fluctuations during the menstrual cycle might acutely change tendon stiffness, but research measuring patellar tendon properties across different cycle phases found no significant differences. The data instead pointed to estrogen having a chronic, long-term influence on tendon behavior rather than an acute one that shifts week to week.12The Journal of Strength & Conditioning Research. Patellar Tendon Properties With Fluctuating Menstrual Cycle Hormones
The Hamstring-to-Quadriceps Balance
One place where sex differences in leg strength become clinically important is the balance between the quadriceps and the hamstrings. These two muscle groups work as antagonists around the knee, and their strength ratio affects both performance and injury risk. A study of 574 ACL-reconstruction patients found that women actually had a higher hamstring-to-quadriceps ratio than men on both the reconstructed and uninjured sides.13PubMed Central. No Association Between Hamstrings-to-Quadriceps Strength Ratio and Second ACL Injuries After Accounting for Prognostic Factors: A Cohort Study of 574 Patients After ACL-Reconstruction That might sound like good news, but the picture shifts depending on how the measurement is taken and at what age.
During adolescence, a significant divergence occurs. Boys show about a 179% increase in hamstring strength with maturation, while girls show only about a 27% increase, meaning mature girls end up with a significantly higher quadriceps-to-hamstring ratio than any other group.14PubMed. Effect of gender and maturity on quadriceps-to-hamstring strength ratio and anterior cruciate ligament laxity A high quad-to-hamstring ratio means the quadriceps can overpower the hamstrings during sudden deceleration or direction changes, putting extra stress on the ACL. When researchers measured functional hamstring-to-quadriceps ratios across different joint angles and movement speeds, women consistently had lower ratios than men, especially near full knee extension and at higher velocities, which are precisely the conditions under which ACL injuries tend to happen.15PubMed. Sex-related differences in joint-angle-specific functional hamstring-to-quadriceps strength ratios
Skeletal geometry compounds the problem. Women tend to have a larger Q-angle, which is the angle formed by the line of pull of the quadriceps relative to the patellar tendon. A larger Q-angle changes the mechanical forces around the knee and has been linked to higher injury risk in female athletes.16PubMed Central. Impact of the Quadriceps Angle on Health and Injury Risk in Female Athletes So the question is not just “how strong are the legs overall” but “how are the individual muscle groups balanced, and what does the skeleton do with that force.”
Neural Drive
Before a muscle contracts, the nervous system has to activate it. The degree to which someone can voluntarily activate a muscle (called voluntary activation) turns out to have sex-specific patterns. During maximal plantar flexion with the knee straight, men achieved about 96% voluntary activation compared with about 88% in women. But during knee extension, the difference was trivially small: about 95% in men versus about 94% in women.17PeerJ. Effects of sex and joint action on voluntary activation This means that for the quadriceps specifically, women can recruit their available muscle nearly as fully as men can. The activation gap shows up more in the calf muscles, which may partly explain why sex differences in calf strength tend to be somewhat larger than those in thigh strength.
How Women and Men Respond to Training
One of the most reassuring findings for anyone who strength-trains is that relative gains from resistance training are remarkably similar between the sexes. After 12 weeks of weight training, men and women both increased their knee extension strength by about 19%. The time course of those gains, and the proportional increases in muscle thickness, were similar for both sexes.18PubMed. Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women Research specifically examining early-phase adaptations confirmed that lower-extremity skeletal muscle adaptations contributing to strength gains were similar for men and women.19PubMed. Skeletal muscle adaptations during early phase of heavy-resistance training in men and women
The practical takeaway: women’s legs respond to training at the same rate as men’s, percentage-wise. A woman who squats twice a week for three months can expect similar relative strength improvements to a man doing the same program. The absolute numbers will still differ because of the different starting points, but the muscle tissue is adapting along the same trajectory.
How Aging Changes the Picture
Leg strength declines with age in both sexes, but not at the same pace. Data from a large longitudinal study found that men lost almost twice as much leg strength as women over time. The annual rate of leg strength decline was about 3.4-4.1% in men versus about 2.6-3.0% in women, depending on race, while both sexes lost leg lean mass at about 1% per year.20The Journals of Gerontology: Series A. The Loss of Skeletal Muscle Strength, Mass, and Quality in Older Adults: The Health, Aging and Body Composition Study Two things stand out here. First, strength declined roughly three times faster than muscle mass in both sexes, meaning something beyond just losing muscle is driving the loss. Second, the gap between men and women narrows with age because men are losing strength faster. Over a span of decades, the sex difference in leg strength shrinks progressively.
This has real implications for independence in older adults. Leg strength is one of the strongest predictors of fall risk, ability to climb stairs, and capacity to live without assistance. Because women start with less absolute strength but lose it more slowly, and because women on average live longer, there is a delicate period where many older women hover near the functional threshold for daily tasks. Strength training in older women is one of the most effective interventions for preserving independence, and the fact that muscle responds to training at similar rates in both sexes throughout life makes this a practical and not merely theoretical recommendation.
Running Economy and Fuel Use
How legs perform during sustained activity involves more than raw force. Running economy, the energy cost of running at a given speed, differs between men and women in a way that depends on how you measure it. At the same absolute speed, women are more economical than men. But when compared at the same relative intensity (the same percentage of their maximal aerobic capacity), men come out ahead.21The Journal of Strength & Conditioning Research. Lower-Body Determinants of Running Economy in Male and Female Distance Runners Meanwhile, when body mass is matched, women show similar energy cost to men despite having different gait patterns.22PubMed. Factors affecting the energy cost of level running at submaximal speed
Women’s legs also fuel themselves differently during sustained effort. During submaximal endurance exercise, women burn substantially more intramuscular fat, with intramuscular fat breakdown accounting for about 25% of total energy use in women versus about 5% in men. Glycogen use, blood glucose uptake, and plasma fatty acid oxidation were similar between the sexes.23PubMed. Gender differences in substrate utilization during submaximal exercise in endurance-trained subjects This greater reliance on intramuscular fat may help spare glycogen, which is a limited resource during prolonged exercise. It is one of the reasons women tend to hold pace better in ultra-endurance events, where glycogen depletion becomes the limiting factor.
Gluteal Muscles and Body Composition
The gluteal muscles deserve separate mention because they are the largest and among the most powerful muscles in the body, and popular belief holds that women have disproportionately stronger glutes. An MRI study of recreational cyclists found that men had larger gluteal muscles in absolute terms, but when muscle volume was normalized to body weight, no differences were found in the gluteus maximus, gluteus medius, or gluteus minimus between men and women. Women did have more subcutaneous fat around the glutes, which contributes to shape differences but not to force production.24PubMed Central. Similarities and differences in skeletal muscle and body composition between sexes: an MRI study of recreational cyclists So the commonly repeated idea that women are “glute dominant” relative to men does not hold up when you measure the actual muscle rather than external appearance.
Carrying Loads
One real-world test of leg function is carrying weight over distance. A study of overground load carriage at self-selected walking speeds found no sex-by-load interactions for any spatial, timing, movement angle, or force variable.25PubMed Central. Mechanical Differences between Men and Women during Overground Load Carriage at Self-Selected Walking Speeds In plain terms, when carrying loads and choosing their own pace, men and women adapted their gait mechanics in the same ways. However, a scoping review of load carriage in female soldiers found that military loads affect biomechanics and physiology differently in women and to a greater extent than in men.26Applied Ergonomics. Biomechanical and physiological effects of female soldier load carriage: A scoping review The distinction matters: when loads are proportionally heavier relative to body weight, as standard military packs tend to be for smaller individuals, the stress on women’s legs is disproportionately greater. The legs themselves are not mechanically different in how they manage the load; the issue is that the load represents a bigger fraction of their capacity.